Torque tube coupler

ABSTRACT

A solar-tracking photovoltaic (PV) system having several PV modules mounted on a torque tube is described. The torque tube may include several sections joined by a torque tube coupler. For example, the torque tube coupler may having a medial section and end sections to join to the torque tube sections. The medial section and the torque tube sections may have a same outer diameter.

BACKGROUND

Some sun-tracking solar power systems, such as utility-scalephotovoltaic installations, are designed to pivot a large number ofsolar modules to track the movement of the sun. For example,sun-tracking solar power systems may include rows of solar modulessupported on respective torque tube assemblies. Each torque tubeassembly may include several long shafts connected together in anend-to-end fashion. Furthermore, each torque tube assembly may be movedby a single motor, controlled by a dedicated controller. A sun-trackingsolar power system may be a single-drive sun-tracking solar powersystem.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a perspective view of a multi-drive solar-trackingphotovoltaic (PV) system, in accordance with an embodiment of thepresent disclosure.

FIG. 2 illustrates an exploded perspective view of a torque tubeassembly, in accordance with an embodiment of the present disclosure.

FIG. 3 illustrates a perspective view of a driven support assembly, inaccordance with an embodiment of the present disclosure.

FIG. 4 illustrates a perspective view of a non-driven support assembly,in accordance with an embodiment of the present disclosure.

FIG. 5A illustrates a perspective view of a motor drive of a drivensupport assembly, in accordance with an embodiment of the presentdisclosure.

FIG. 5B illustrates a section view of a motor drive of a driven supportassembly in accordance with an embodiment of the present disclosure.

FIG. 6 illustrates a perspective view of a bearing assembly of anon-driven support assembly, in accordance with an embodiment of thepresent disclosure.

FIG. 7 illustrates a perspective view of a torque tube coupler, inaccordance with an embodiment of the present disclosure.

FIG. 8 illustrates a perspective section view of a torque tube coupler,in accordance with an embodiment of the present disclosure.

FIG. 9 illustrates a perspective view of an end section of a torque tubecoupler, in accordance with an embodiment of the present disclosure.

FIG. 10 illustrates a section view of a torque tube coupler joined to atorque tube, in accordance with an embodiment of the present disclosure.

FIG. 11 illustrates a section view, taken about line 11-11 of FIG. 10,of a torque tube coupler joined to a torque tube, in accordance with anembodiment of the present disclosure.

FIGS. 12-14 illustrate flowcharts of various methods of operating amulti-drive solar-tracking PV system, in accordance with an embodimentof the present disclosure.

DETAILED DESCRIPTION

The following detailed description is merely illustrative in nature andis not intended to limit the embodiments of the subject matter or theapplication and uses of such embodiments. As used herein, the word“exemplary” means “serving as an example, instance, or illustration.”Any implementation described herein as exemplary is not necessarily tobe construed as preferred or advantageous over other implementations.Furthermore, there is no intention to be bound by any expressed orimplied theory presented in the preceding technical field, background,brief summary or the following detailed description.

This specification includes references to “one embodiment” or “anembodiment.” The appearances of the phrases “in one embodiment” or “inan embodiment” do not necessarily refer to the same embodiment.Particular features, structures, or characteristics may be combined inany suitable manner consistent with this disclosure.

Terminology. The following paragraphs provide definitions and/or contextfor terms found in this disclosure (including the appended claims):

“Comprising.” This term is open-ended. As used in the appended claims,this term does not foreclose additional structure or steps.

“Configured To.” Various units or components may be described or claimedas “configured to” perform a task or tasks. In such contexts,“configured to” is used to connote structure by indicating that theunits/components include structure that performs those task or tasksduring operation. As such, the unit/component can be said to beconfigured to perform the task even when the specified unit/component isnot currently operational (e.g., is not on/active). Reciting that aunit/circuit/component is “configured to” perform one or more tasks isexpressly intended not to invoke 35 U.S.C. § 112, sixth paragraph, forthat unit/component.

“First,” “Second,” etc. As used herein, these terms are used as labelsfor nouns that they precede, and do not imply any type of ordering(e.g., spatial, temporal, logical, etc.). For example, reference to a“first” motor drive does not necessarily imply that this motor drive isthe first motor drive in a sequence; instead the term “first” is used todifferentiate this motor drive from another motor drive (e.g., a“second” motor drive).

“Coupled”—The following description refers to elements or nodes orfeatures being “coupled” together. As used herein, unless expresslystated otherwise, “coupled” means that one element/node/feature isdirectly or indirectly joined to (or directly or indirectly communicateswith) another element/node/feature, and not necessarily mechanically.

In addition, certain terminology may also be used in the followingdescription for the purpose of reference only, and thus are not intendedto be limiting. For example, terms such as “upper,” “lower,” “above,”“below,” “in front of,” and “behind” refer to directions in the drawingsto which reference is made. Terms such as “front,” “back,” “rear,”“side,” “outboard,” “inboard,” “leftward,” and “rightward” describe theorientation and/or location of portions of a component, or describe therelative orientation and/or location between components, within aconsistent but arbitrary frame of reference which is made clear byreference to the text and the associated drawings describing thecomponent(s) under discussion. Such terminology may include the wordsspecifically mentioned above, derivatives thereof, and words of similarimport.

“Inhibit”—As used herein, inhibit is used to describe a reducing orminimizing effect. When a component or feature is described asinhibiting an action, motion, or condition it may completely prevent theresult or outcome or future state completely. Additionally, “inhibit”can also refer to a reduction or lessening of the outcome, performance,and/or effect which might otherwise occur. Accordingly, when acomponent, element, or feature is referred to as inhibiting a result orstate, it need not completely prevent or eliminate the result or state.

Although many of the examples described herein are for solar-trackingphotovoltaic (PV) systems, the techniques and structures may applyequally to other non-solar-tracking or stationary solar energycollection systems, as well as concentrated thermal solar systems, etc.Moreover, although much of the disclosure is described in terms ofground-mounted solar-tracking solar energy collection installations, thedisclosed techniques and structures apply equally to other solar energycollection installations, e.g., rooftop solar installations.

Existing single-drive sun-tracking solar power systems use a singlemotor to rotate an end of a torque tube assembly to transmit torque toan opposite end of the torque tube assembly. A single motor may also beused to rotate a center location of a torque tube assembly to transmittorque to a longitudinal separated location. An overall torsionalstiffness of such systems is therefore governed in part by a length ofthe torque tube assembly, and the length can be on a scale of onehundred feet or more. PV modules mounted on the torque tube assembly mayexperience high wind loads that can excite a structure of the solarpower system. More particularly, winds may apply drag to the PV modules,which can twist the torque tube. Such twisting is a function of thetorque tube stiffness, and thus, single-drive systems may fail unlesstorque tube lengths are minimized or torque tube sizes, e.g., wallthicknesses, are maximized to increase stiffness. Decreasing torque tubelengths reduces a potential energy collection of the system, however,and increasing torque tube size increases system cost. Accordingly,single-drive sun-tracking solar power systems have substantial systemlimitations.

In an aspect, a multi-drive solar-tracking PV system includes severaldrives inputting torque to a same torque tube at longitudinallyseparated locations. More particularly, the drives may be separated by adistance such that a span between driven supports maintains a systemstiffness above a predetermined threshold. For example, the span betweendrives may be less than one hundred feet between adjacent drives of thesystem. Accordingly, a span between ends of a torque tube section may beeffectively reduced to avoid wind excitation, e.g., by winds with speedsup to ninety miles per hour.

In an aspect, a torque tube assembly of a multi-drive solar-tracking PVsystem includes several torque tube segments coupled by an intermediatetorque tube coupler. Each torque tube segment may have an overall lengthless than 40 feet (12 meters), such that the torque tube segments aretransportable in standard shipping containers. Furthermore, the torquetube coupler may have a closed wall section profile, such that torsionand bending stresses are distributed throughout the cross-sectionalarea, and the torque tube assembly robustly transmits torque betweentorque tube segments.

The aspects described above may be realized by the multi-drivesolar-tracking PV system disclosed herein. In the following description,numerous specific details are set forth, such as specific materialregimes and component structures, in order to provide a thoroughunderstanding of embodiments of the present disclosure. It will beapparent to one skilled in the art that embodiments of the presentdisclosure may be practiced without these specific details. In otherinstances, well-known fabrication techniques or component structures,such as specific types of actuators or techniques for coupling suchactuators with system components, are not described in detail in orderto not unnecessarily obscure embodiments of the present disclosure.Furthermore, it is to be understood that the various embodiments shownin the figures are illustrative representations and are not necessarilydrawn to scale.

By way of summary, disclosed herein is a solar-tracking PV system havinga torque tube assembly including a first torque tube segment coupled toa second torque tube segment by a torque tube coupler. The torque tubecoupler may extend along a longitudinal axis between end sections thatare coupled to respective free ends of the torque tube segments. In anembodiment, an outer diameter of a medial section of the torque tubecoupler is a same diameter as respective outer diameters of the torquetube segments. Accordingly, PV modules may be mounted on the torque tubesegments and the torque tube coupler using the same fastening hardware,and the torque tube coupler may transmit torque between the torque tubesegments.

Referring to FIG. 1, a perspective view of a multi-drive solar-trackingPV system is shown in accordance with an embodiment of the presentdisclosure. An electricity farm may include one or more solar-trackingPV systems 100. Solar-tracking PV system 100 may be considered amulti-drive system because several motor drives may be coupled to a sametorque tube to input torque to the torque tube at longitudinallyseparated locations. For example, solar-tracking PV system 100 may be adual-drive system having a pair of motor drives coupled to respectiveends of the same torque tube 104, or torque tube section. In anembodiment, solar-tracking PV system 100 includes several driven supportassemblies 102 supporting a torque tube 104 above the ground at thelongitudinally separated locations. For example, solar-tracking PVsystem 100 may include a first driven support assembly 106longitudinally separated from a second driven support assembly 108 in adirection of a longitudinal axis 110.

Several PV modules 112 may be mounted on torque tube 104 alonglongitudinal axis 110. For example, solar-tracking PV system 100 mayinclude a row of tens of solar modules arranged in a series. The seriesmay include, for example, 70-100 PV modules 112 between a first outwardend 130 and a second outward end 132. Each PV module 112 may include oneor more solar collecting devices. For example, each PV module 112 mayinclude a PV laminate mounted on a PV frame. The PV laminates may beconfigured to receive sunlight for conversion into electrical energy.For example, the PV laminates may include one or more PV cells laminatedbetween an optically transparent upper cover and/or back cover.

Each PV frame may support a respective PV laminate along an outerperimeter and/or a back surface of the laminate structure. The PV framemay be mounted on torque tube 104 using mounting holes in the torquetube 104 components, as described below.

In an embodiment, torque tube 104 is supported above the ground by oneor more non-driven support assemblies 118. For example, a non-drivensupport assembly 118 may be positioned longitudinally between firstdriven support assembly 106 and second driven support assembly 108. Eachnon-driven support assembly 118 along longitudinal axis 110 of torquetube 104 may support and allow for rotation of torque tube 104 about thelongitudinal axis 110 without inputting torque to torque tube 104. Thus,non-driven support assemblies 118 may facilitate a stable rotation oftorque tube 104 without actually driving such rotation.

Driven support assemblies may affect rotation of torque tube 104 aboutlongitudinal axis 110 based on electrical inputs provided or controlledby a controller 120. Controller 120 may include a microprocessor orcomputer configured to control the delivery of electrical power tomotors of driven support assemblies along torque tube 104. For example,controller 120 may directly or indirectly, e.g., through control of apower supply, deliver a first electrical power input 122 to first drivensupport assembly 106 and a second electrical power input 124 to seconddriven support assembly 108. Accordingly, the motors and/or mechanicaltransmission components of the driven support assemblies may besimultaneously controlled by controller 120 to input torque to first end114 and second end 116 of a section of torque tube 104. Moreparticularly, driven support assemblies may apply the torque to firstend 114 and second end 116 about longitudinal axis 110. Thus, torquetube 104 may pivot or rotate about longitudinal axis 110 such that PVmodules 112 track a solar source, e.g., the sun or a reflective surfaceredirecting sunrays toward PV modules 112.

Referring to FIG. 2, an exploded perspective view of a torque tubeassembly is shown in accordance with an embodiment of the presentdisclosure. Each driven section of torque tube 104 may be furthersegmented into several tube sections. For example, torque tube 104 mayhave at least two tubular sections between first end 114 and second end116. More particularly, a first torque tube 202, which may be a firstsection of torque tube 104, may have a first driven end 204, and asecond torque tube 206, which may be a second section of torque tube104, may have a second driven end 208. PV modules 112 may be mounted onfirst torque tube 202 and second torque tube 206 in a same manner thatPV modules 112 are mounted on a singular torque tube, i.e., anon-segmented torque tube.

In an embodiment, a length 210 of each torque tube 104 section may havea predetermined upper limit. For example, the tube sections may be nolonger than a standard shipping container. Standard shipping containersmay typically have lengths of forty feet. Thus, each tube section mayhave a length 210 less than 40 feet (12 meters), e.g., 30-39 feet(9.1-11.9 meters), to maximize a length of each tube section and toallow tube sections to be shipped to remote geographies forinstallation.

Whereas length 210 of the tube sections, e.g., first torque tube 202 andsecond torque tube 206, may be limited to less than 40 feet, an overalllength of torque tube 104 between first driven end 204 and second drivenend 208 may be more than 40 feet. Accordingly, the tube sections may bejoined at one or more joint 212. For example, first torque tube 202 mayextend along longitudinal axis 110 from first driven end 204 to a firstfree end 214. Similarly, second torque tube 206 may extend alonglongitudinal axis 110 from second driven end 208 to a second free end216. Second free end 216 may be coupled to first free end 214 by a weld,a fastener joint, or other manners and mechanisms of joining tubes toextend an overall length of torque tube 104 beyond the individual length210 of the respective tube sections.

Still referring to FIG. 2, first free end 214 of first torque tube 202may be coupled to second free end 216 of second torque tube 206 by atorque tube coupler 218. Torque tube coupler 218 may be configured tojoin several torque tube 104 segments and may include a structure toresist loading that is particular to multi-tube joints. For example,torque tube coupler 218 may provide joint 212 having a closed wallsection, as described below. By comparison, other tube-joiningmechanisms having open wall sections, such as a dual-collar mechanismhaving two semi-cylindrical plates joined on either side of joint 212,could fail under a same bending or torsion load. Various embodiments oftorque tube coupler 218 are described with respect to FIGS. 7-11 below.

Referring to FIG. 3, a perspective view of a driven support assembly isshown in accordance with an embodiment of the present disclosure. Drivensupport assembly 102 shown in FIG. 3 may be representative of eachdriven support assembly 102 of solar-tracking PV system 100, e.g., firstdriven support assembly 106 and second driven support assembly 108. Eachdriven support assembly 102 may include a supportive stand, such as adrive pile 302. Drive pile 302 may be a columnar structure, such as anI-beam, having a lower end 304 driven into the ground, and an upper end306 supporting an actuator configured to provide a mechanical torque totorque tube 104. More particularly, each drive pile 302 may carry arespective rotational actuator, such as a motor drive 308. An embodimentof motor drive 308 is described below with respect to FIGS. 5A-5B. Thus,first driven support assembly 106 may include a first motor drive 308,and second driven support assembly 108 may include a second motor drive308, and the motor drives may be mounted on respective drive piles 302.Furthermore, it follows from the description above that the first motordrive 308 may be coupled to first end 114 of torque tube 104, e.g.,first driven end 204 of first torque tube 202, and the second motordrive 308 may be coupled to second end 116 of torque tube 104, e.g.,second driven end 208 of second torque tube 206. Accordingly, firsttorque tube 202 may be supported by first driven support assembly 106,and second torque tube 206 may be supported by second driven supportassembly 108.

Referring to FIG. 4, a perspective view of a non-driven support assemblyis shown in accordance with an embodiment of the present disclosure.Non-driven support assembly 118 shown in FIG. 4 may be representative ofeach non-driven support assembly 118 of solar-tracking PV system 100.For example, non-driven support assembly 118 may be one of severalnon-driven support assemblies 118 located longitudinally between firstdriven support assembly 106 and second driven support assembly 108. Eachnon-driven support assembly 118 may include a supportive stand, such asa non-drive pile 402. Non-drive pile 402 may have a similar structure todrive pile 302. For example, non-drive pile 402 may be a columnarstructure such as an I-beam, or a post having a round or rectangularcross-sectional profile. The columnar structure of non-drive pile 402may be different than drive pile 302, however. For example, non-drivepile 402 may include a different beam type including a differentcross-sectional geometry having a web portion and a flange portion,e.g., a “C” or “Z” shaped profile. Each non-drive pile 402 may carry arespective supportive mechanism, such as a bearing assembly 404. Anembodiment of bearing assembly 404 mounted on non-drive pile 402 isdescribed below with respect to FIG. 6.

Drive pile 302 and non-drive pile 402 may be columnar structures otherthan beams having web portions and flange portions. For example, thepiles 302, 402 may be tubular or solid posts. The piles 302, 402 may besymmetric or asymmetric about a vertical axis. Accordingly, piles 302,402 may be of any elongated beam type.

Referring to FIG. 5A, a perspective view of a motor drive of a drivensupport assembly is shown in accordance with an embodiment of thepresent disclosure. Each driven support assembly 102 may include a motordrive 308 mounted on upper end 306 of drive pile 302. Motor drive 308may be configured to convert electrical power input into a mechanicaltorque output. More particularly, motor drive 308 may output torquedirectly to a driven end, e.g., first driven end 204, of torque tube104. Accordingly, motor drive 308 may include a gearbox 502 having anoutput coupling that connects directly to first driven end 204. That is,gearbox 502 may include a rotational output attached to first driven end204 to rotate torque tube 104 about longitudinal axis 110.

In an embodiment, gearbox 502 includes a worm drive coupled to therotational output. More particularly, gearbox 502 of motor drive 308 mayinclude a worm gear driven by a worm (not shown). Worm drives are knownin the art, and thus further description of particular worm driveconfigurations is not provided here. The worm gear may be mounted withina gearbox housing, and the worm gear may be arranged along longitudinalaxis 110 and coupled to the rotational output to input torque to firstdriven end 204 of torque tube 104.

The worm of gearbox 502 may be coupled to an input actuator, such as agearmotor 504. Gearmotor 504 may deliver torque to worm through anoutput shaft. Thus, electrical power input delivered to gearmotor 504may be converted into input torque to the worm, and the input torque maybe transmitted from the worm to the worm gear to output mechanicaltorque to first driven end 204. It will be appreciated that gearmotor504 may be electrically coupled to controller 120, and controller 120may manage the delivery of electrical power to gearmotor 504 to controlthe output torque delivered to torque tube 104.

Referring to FIG. 5B, a section view of a motor drive of a drivensupport assembly is shown in accordance with an embodiment of thepresent disclosure. Gearbox 502 of motor drive 308 may include a wormdrive 512 to transmit power from gearmotor 504 to a torque tubecoupling. More particularly, worm drive 512 may be coupled to torquetube 104 by torque tube coupling. Worm drive 512 may include a worm 514(drawn schematically) to receive input torque from gearmotor 504, and aworm gear 516 (drawn schematically) to output transmitted torque to thetorque tube coupling. Worm 514 and worm gear 516 may be constructed asis known in the art, and thus, particular description of the componentsis omitted in the interest of brevity. It will be appreciated, however,that worm 514 may rotate about a worm axis 518, and worm gear 516 mayrotate about longitudinal axis 110. Accordingly, worm axis 518 may bebelow longitudinal axis 110, and correspondingly, below torque tube 104.

In an embodiment, gearmotor 208 includes a planetary gear train 520coupled to worm 514. For example, planetary gear train 520 may bedisposed within a mounting cavity 522 of a gearbox housing 523. That is,a cavity wall 531 may extend around mounting cavity 522 about worm axis518, and an output of planetary gear train 520 may be coupled to worm514 within mounting cavity 522. Thus, planetary gear train 520 may besupported by a housing mount 550 within mounting cavity 522 along wormaxis 518.

As described below, gearmotor 504 may include an offset gear (not shown)coupled to planetary gear train 520, and coupled to a pinion gear 524 ofmotor assembly 552. For example, motor assembly 552 may include piniongear 524 mounted on an output shaft 526 of a motor 528, and the offsetgear may transmit mechanical power from pinion gear 524 to planetarygear train 520. The offset gear may have an internal gear portion, e.g.,an internal spur gear, engaged with planetary gear train 520 about wormaxis 518 and an external gear portion, e.g., an external spur gear,engaged with pinion gear 524 adjacent to shaft axis 530. Thus, theoffset gear may transmit power laterally between pinion gear 524 onshaft axis 530 and planetary gear train 520 on worm axis 518.

Output shaft 526 may extend along a vertical plane, and planetary geartrain 520 may extend along the vertical plane. For example, worm axis518 and shaft axis 530 may be contained within the vertical plane, andthus planetary gear train 520 and output shaft 526 may be aligned alongthe same vertical plane. Furthermore, planetary gear train 520 may bevertically above shaft axis 530 within the vertical plane. Accordingly,output shaft 526 may rotate about shaft axis 530 offset below worm axis518. For example, shaft axis 530 may be offset below worm axis 518 by adistance equal to a radius of the offset gear plus a radius of piniongear 524. As such, the offset gear lowers motor assembly 552 relative toworm drive 512, and increases a clearance between motor assembly 406 andPV module 112 mounted on torque tube 104.

Referring to FIG. 6, a perspective view of a bearing assembly of anon-driven support assembly is shown in accordance with an embodiment ofthe present disclosure. Each non-driven support assembly 118 may includea bearing assembly 404 mounted on non-drive pile 402. Bearing assembly404 may include a bearing housing 602 supporting a bearing 604.Furthermore, bearing 604 may extend around longitudinal axis 110 tosupport torque tube 104. For example, bearing 604 may have an annularstructure formed from a low friction material, and torque tube 104 mayextend through an inner diameter of the annular bearing 604. Thus,bearing 604 may constrain transverse movement of torque tube 104 andpermit torque tube 104 to rotate about longitudinal axis 110 when motordrive 308 inputs torque to the respective driven end.

Distributing driven and non-driven support assemblies along torque tube104 can provide several benefits. For example, the distribution of inputtorque at longitudinally separated locations can increase an effectivesystem stiffness by shortening torque tube section lengths betweendrives, and thus, an angular deflection of torque tube 104 under a givenwind loading may be minimized. The increase in effective systemstiffness may also allow for a thinner torque tube 104 to be used. Forexample, a wall thickness of the torque tube 104 may be reduced, ascompared to a single-drive system torque tube 104. Accordingly, alikelihood of wind damage may be reduced and/or larger PV modules 112may be used for a designed wind load to increase system energyproduction. This may be achieved even with a lighter, less costly,torque tube. In an embodiment, torque tube 104 has a cylindrical wallwith a thickness less than 0.75 cm. A diameter of torque tube 104 havingsuch a wall thickness may be greater than 10 cm. Since the weight oftorque tube 104 and PV modules 112 mounted on torque tube 104 may bedistributed across more and/or more evenly spaced support assemblies, apile size and weight of the driven support assemblies may also bereduced. Accordingly, a multi-drive solar-tracking PV system 100 may bemore robust and less costly to manufacture or install, as compared totypical single-drive systems.

As described above, a dual-drive solar-tracking PV system 100 mayinclude a torque tube 104 having several segments joined at joint 212between adjacent driven support assemblies. Furthermore, joint 212between torque tube 104 segments can resist bending and torsiongenerated by wind loading. Joint 212, for example, may include torquetube coupler 218.

Referring to FIG. 7, a perspective view of a torque tube coupler isshown in accordance with an embodiment of the present disclosure. Torquetube coupler 218 may have a tubular construction that includes swagedand/or expanded ends. For example, torque tube coupler 218 may include agalvanized steel tube necked end sections that fit into an innerdiameter of one or more segments of torque tube 104. Torque tube coupler218 may have a predetermined length less than length 210 of torque tube104 sections. For example, whereas each torque tube section adjoined bytorque tube coupler 218 may have an overall length in a range of 30-40feet, e.g., 39 feet, torque tube coupler 218 may have an overall lengthbetween 4-14 feet, e.g., 9 feet.

Torque tube coupler 218 may include a medial section 702 to extendbetween adjacent free ends of adjoining torque tube 104 sections. In anembodiment, torque tube coupler 218 supports one or more PV modules 112,and thus, medial section 702 may have a medial outer diameter 704 thatis similar to an outer diameter of torque tube 104. For example, medialouter diameter 704 and the outer diameter of torque tube 104 may beequal and in a range of 5-10 inches, e.g., 6.6 inches. Accordingly, PVframes may be mounted on torque tube coupler 218 in a same manner thatis used to mount PV modules 112 on torque tube 104.

Torque tube coupler 218 may include several end sections 705 extendingfrom opposite ends of medial section 702. For example, a first endsection 706 may extend along longitudinal axis 110 to attach to an endof first torque tube 202, e.g., first free end 214, and a second endsection 708 may extend along longitudinal axis 110 to attach to an endof second torque tube 206, e.g., second free end 216. Each end section705 may include an end outer diameter 710 configured to mate with anadjoining torque tube section, as described below. Accordingly, medialsection 702 may extend between first end section 706 and second endsection 708, and medial outer diameter 704 may be different than endouter diameter 710. For example, medial section 702 may have a sameouter diameter as torque tube 104, and the end sections 705 may havedifferent outer diameters than torque tube 104.

Referring to FIG. 8, a perspective section view of a torque tube coupleris shown in accordance with an embodiment of the present disclosure.Medial section 702 and end sections 705 of torque tube coupler 218 mayhave continuous walls surrounding longitudinal axis 110. For example,medial section 702 may include a medial wall 802 extending aroundlongitudinal axis 110, and each end section 705 may include an end wall804 extending around longitudinal axis 110. A thickness of the walls maybe the same or different. For example, a wall thickness of medial wall802 and/or end walls 804 may all be in a range of 9-11 gauge.

Referring to FIG. 9, a perspective view of an end section of a torquetube coupler is shown in accordance with an embodiment of the presentdisclosure. Torque tube coupler 218 may include several holes in one ormore sections to serve various functions in the assembly of torque tube104. For example, medial section 702 may include a medial mounting hole712 (FIG. 7) through medial wall 802. Medial mounting hole 712 mayreceive a fastener, e.g., a bolt or a rivet, to attach a PV module 112to medial section 702. Similarly, one or more of the end sections 705,e.g., second end section 708, may include an end mounting hole 902through end wall 804. As described below, end mounting hole 902 mayreceive a fastener to simultaneously attach a PV module 112 to endsection 705 and torque tube 104.

In an embodiment, each end wall 804 of the end sections 705 includesseveral fastener holes 904. Fastener holes 904 may be distributed arounda circumference of the end section 705. Fastener holes 904 may beequally spaced around the circumference along a transverse planeorthogonal to longitudinal axis 110. For example, end section 705 mayinclude eight fastener holes 904 distributed at intervals of 45 degreesaround longitudinal axis 110. Fastener holes 904 may align with matingholes in the ends of torque tube 104 sections. Thus, fasteners may beinserted through fastener holes 904 in both end section 705 and torquetube 104 to connect torque tube coupler 218 two torque tube 104.

Medial section 702 may be coupled to one or more end section 705 by arespective transition section 906. Transition section 906 may include anouter surface that transitions between an inward end 908 at medialsection 702 to an outward end 910 at end section 705. Thus, transitionsection 906 may be coupled to medial section 702 at inward end 908 andto end section 705 at outward end 910. Outward end 910 and inward end908 may have different outer dimensions, e.g., diameters. For example,end section 705 may be formed by swaging an end of a uniform tube, andthus, end section 705 may effectively be a necked down portion of medialsection 702. Alternatively, end section 705 may be formed by expandingan end of the uniform tube, or swaging a metal portion of the uniformtube. A profile of the outer surface of transition section 906 maydepend on the swaging or expansion process, and by way of example,transition section 906 may have a tapered or stepped profile. Moreparticularly, transition section 906 may taper smoothly and continuouslyfrom a larger diameter at inward end 908 to a smaller diameter atoutward end 910.

The holes of torque tube coupler 218 may have predetermined positionsrelative to each other. For example, medial mounting hole 712 and endmounting hole 902 may be aligned along a longitudinal plane containinglongitudinal axis 110. The longitudinal plane may be a plane, forexample, that bisects torque tube coupler 218 longitudinally such thatthe sectioned torque tube coupler 218 would appear as shown in theperspective section view of FIG. 8. As such, a PV module 112 may bemounted on torque tube coupler 218 using fasteners that are aligned in alongitudinal direction.

Referring to FIG. 10, a section view of a torque tube coupler joined toa torque tube is shown in accordance with an embodiment of the presentdisclosure. End section 705 is coupled to an end of torque tube 104. Forexample, torque tube coupler 218 may be coupled to first free end 214 offirst torque tube 202 or to second free end 216 of second torque tube206. In an embodiment, end section 705 is inserted into the end oftorque tube 104. For example, end outer diameter 710 may be less than aninner diameter of torque tube 104, allowing end section 705 to beinserted into an inner diameter of torque tube 104. Both end sections705 of torque tube coupler 218 may be similarly fit into respectivetorque tube 104 sections. Thus, first torque tube 202, second torquetube 206, and torque tube coupler 218 may extend along longitudinal axis110 and be pivotable about longitudinal axis 110. Fasteners may bedisposed within mating fastener holes 904 of torque tube 104 and endsection 705 to transmit torque between the tubular structures.Similarly, fasteners may be inserted through end mounting holes 902 inboth end section 705 and torque tube 104 to transmit torque from thetubular structures to a PV module 112 mounted on the tubular structures.

In an embodiment, medial outer diameter 704 may be the same as a torquetube coupler 218 outer diameter 1002. PV frame may be mounted on outsidesurfaces of torque tube coupler 218 and torque tube 104 that are equallyspaced apart (at a same radial distance) from longitudinal axis 110. Asa result, PV frame may be attached to both torque tube coupler 218 andtorque tube 104 using a same type of coupling. That is, by keeping theouter dimension the same along an entire length of the torque tubeassembly, the need for different module attachment couplings isobviated. Thus, a PV module 112 may be mounted on both torque tubecoupler 218 and an adjacent torque tube 104, e.g., second torque tube206, using the same mounting hardware.

Torque tube coupler 218 and torque tube 104 may have similar wallthicknesses, and thus, end outer diameter 710, which may be the samediameter as outward end 910 of transition section 906, may be less thana medial inner diameter 1004 of medial section 702. More particularly,when medial section 702 and torque tube 104 have a same wall thickness,it follows that for an outer diameter of end section 705 to fit withintorque tube 104, end outer diameter 710 is less than both the innerdiameter of torque tube 104 and medial inner diameter 1004.

Referring to FIG. 11, a section view, taken about line 11-11 of FIG. 10,of a torque tube coupler joined to a torque tube is shown in accordancewith an embodiment of the present disclosure. End sections 705 of torquetube coupler 218 and mating portions of the torque tubes 104, e.g., thefree ends of first torque tube 202 and second torque tube 206, mayinclude respective cross-sectional areas of closed wall sections 1102.For example, the closed wall sections 1102 may have cross-sectionalareas that are annular. By way of example, first end section 706 oftorque tube coupler 218 may include a coupler cross-sectional area 1104.Similarly, by way of example, first torque tube 202 may include acorresponding tube cross-sectional area 1106 at first free end 214. Thatis, coupler cross-sectional area 1104 and tube cross-sectional area 1106may be concentrically disposed about longitudinal axis 110.

The concentric annular cross-sectional areas of end section 705 andtorque tube 104 may have dimensions corresponding to an assembledconfiguration in which end section 705 inserts into torque tube 104, orin which end section 705 fits around an outside of torque tube 104. Forexample, when end sections 705 are swaged to a smaller size than medialsection 702, end sections 705 include respective outer diameters thatare less than respective inner diameters of the concentric annularcross-sectional areas of the torque tube 104 ends. That is, end outerdiameter 710 may be less than a tube inner diameter 1108 of tubecross-sectional area 1106.

In an embodiment, end section 705 may fit around torque tube 104. Forexample, end sections 705 may be flared outward to fit around an outerdiameter 1002 of tube cross-sectional area 1106. It will be appreciatedthat in such case the annular cross-sectional areas of the end sections705 include respective inner diameters, i.e., end inner diameters 1108,greater than respective outer diameters 1002 of the concentric annularcross-sectional areas of the torque tube 104 ends. Accordingly, varioustorque tube coupler 218 configurations may be used to interconnecttorque tube 104 sections while maintaining a uniform outer diameter fortorque tube assembly and effectively transmitting torque from firsttorque tube 202 to second torque tube 206 through torque tube coupler218.

As described above, a single controller 120 may control several motordrives 308. For example, controller 120 may be electrically connected toa first motor drive 308 attached to first driven end 204 of first torquetube 202, and controller 120 may be electrically connected to a secondmotor drive 308 attached to second driven end 208 of second torque tube206. Accordingly, the gearmotors 504 of the respective motor drives 308may be controlled by controller 120 to input power to a singular torquetube 104 and/or a torque tube assembly.

Controller 120 may simultaneously control the pair of motor drives 308by controlling the delivery of electrical power to the gearmotors 504 toachieve a desired torque at the longitudinally separated input locationson torque tube 104. More particularly, controller 120 may independentlycontrol the motor drives 308 to input a same or a different torque ateach end of the torque tube 104.

Referring to FIG. 12, a flowchart of various methods of operating amulti-drive solar-tracking PV system 100, is shown in accordance with anembodiment of the present disclosure. At operation 1202, a firstelectrical power input 122 may be delivered to a first motor drive 308.More particularly, electrical power may be delivered to a gearmotor 504of first motor drive 308. Similarly, at operation 1204, a secondelectrical power input 124 may be delivered to a second motor drive 308.More particularly, electrical power may be delivered to a gearmotor 504of second motor drive 308. At operation 1206, the independentlydelivered first electrical power input 122 and second electrical powerinput 124 may be converted by the respective motor drives 308 intorespective mechanical torques. That is, gearmotor 504 of the motor drive308 may convert the electrical power input to a mechanical torque at anoutput shaft, and the output mechanical power may be transmitted to theworm gear of the gearbox 502 and the output of the motor drive 308. Forexample, when first electrical power input 122 is equal to secondelectrical power input 124, and assuming identical efficiencies of thepair of motor drives 308, an identical torque may be generated at theoutput of the first motor drive 308 and the output of the second motordrive 308. At operation 1208, the mechanical torques generated by thepair of motor drives 308 may be applied to respective driven ends oftorque tube 104. Thus, torque tube 104 of multi-drive solar-tracking PVsystem 100 may rotate about longitudinal axis 110 such that solarmodules track the solar source.

Referring to FIG. 13, a flowchart of various methods of operating amulti-drive solar-tracking PV system, is shown in accordance with anembodiment of the present disclosure. Controller 120 may be a “smart”controller configured to diagnose efficiencies in the motor drives 308.At operations 1302 and 1304, first electrical power may be input to thefirst motor drive 308, and second electrical power may be input to thesecond motor drive 308. The motor drives 308 may include powertransmission components such as gearmotor 504, which may be a steppermotor, and gearbox 502, which may essentially be a gearbox including aworm drive. Since the power transmission components may have a knownefficiency, e.g., a design efficiency or an experimentally determinedefficiency, an electrical power input requirement to achieve apredetermined torque or movement of torque tube 104 may be determined.At operation 1306, first electrical power input 122 and secondelectrical power input 124 may be monitored. For example, controller 120may servo a power supply and/or directly measure the electrical powerbeing delivered to the motor drives 308 to determine the electricalpower input values. System characteristics may be derived from theelectrical power input data gathered through the monitoring.

Other feedback signals may be collected by the controller 120 todetermine motor drive 308 performance. For example, in addition tosensing electrical power input to the motor drives 308, controller 120may receive feedback from sensors that monitor torque applied by wind,wind speed and direction, and misalignment of system components. Anycharacteristic relevant to system performance or efficiency may besensed, and corresponding sensor data may be provided to controller 120.

At operation 1308, a relative performance of the motor drives 308 may bedetermined based on the monitored system characteristics, e.g., theelectrical power inputs. For example, when the required electrical inputto achieve a predetermined torque exceeds a threshold value, it may bedetermined that there is a problem with the motor drives 308. Forexample, the stepper motor of gearmotor 504 and/or gears within gearbox502 may be failing. Such a diagnosis may be made through comparisonbetween first electrical power input 122 and second electrical powerinput 124. For example, when the first motor drive 308 demands moreelectrical power than the second motor drive 308 to achieve apredetermined torque, it may be determined that a component of the firstmotor drive 308 is failing. Thus, a relative performance of the motordrives 308 may be determined to trigger a system maintenance procedure.Other system issues that may be determined by monitoring and comparingrequired motor power includes: identifying a stalled motor, identifyinga presence of tracker obstructions, identifying a gearbox failure,identifying an electrical circuit interruption, e.g., in an electricalpower line between controller 120 and the motor drive 308, andidentifying possible misalignment or drift between motor drives 308.

Referring to FIG. 14, a flowchart of various methods of operating amulti-drive solar-tracking PV system, is shown in accordance with anembodiment of the present disclosure. In an embodiment, controller 120independently controls the motor drives 308 to input different torquesto opposite ends of torque tube 104. At operations 1402 and 1404, firstelectrical power may be input to the first motor drive 308, and secondelectrical power may be input to the second motor drive 308. In anembodiment, first electrical power input 122 is different than secondelectrical power input 124. At operation 1406, the different electricalpower inputs are converted by the motor drives 308 into respectivemechanical torques. For example, a torque generated at an output shaftof the gearmotor 504 of the first motor drive 308 may differ from atorque generated at an output shaft of the gearmotor 504 of the secondmotor drive 308. The difference in torque may be proportional to thedifference in electrical power input to the gearmotors 504. Thedifferent output shaft torques may be transmitted through the motordrives 308. Thus, at operation 1408, a first mechanical torque may beapplied by the first motor drive 308 to first driven and a first torquetube 202. Similarly, at operation 1410, a second mechanical torque,different than the first mechanical torque, may be applied by secondmotor drive 308 to second driven end 208 of second torque tube 206. Theindependently controlled motor drives 308 may therefore input differenttorques to first end 114 and second end 116 of torque tube 104. As aresult, a net torsion may be applied to torque tube 104 to twist torquetube 104 between first end 114 and second end 116. As torque tube 104twists, a relative pitch of PV modules 112 mounted on torque tube 104may be altered. For example, whereas the front surfaces of several PVmodules 112 mounted on torque tube 104 may be parallel when torque tube104 has no net torsion, twisting of torque tube 104 may rotaterespective mounting points of the PV modules 112 about longitudinal axis110 such that the front surfaces are no longer parallel when torque tube104 is twisted.

A net torsion may be introduced into torque tube 104 either by applyingdifferent torques to first end 114 and second end 116 in a samedirection, or by applying torques in opposite directions at first end114 and second end 116. Twisting torque tube 104 as described above maybe used to achieve several functional advantages. For example, changingthe pitch of PV modules 112 relative to each other may change winddynamics such that less wind drag is applied to the entire PV system,and thus, a likelihood of system failure under wind loading may bereduced. Also, altering the pitch of PV modules 112 may prevent shadingof one PV laminate by another PV laminate. For example, moving the otherPV laminate may shift the shading profile to reduce a total amount ofshading and increase a solar energy collection of the system.

A solar-tracking PV system including a torque tube assembly havingseveral segments coupled by a torque tube coupler has been described.Although specific embodiments have been described above, theseembodiments are not intended to limit the scope of the presentdisclosure, even where only a single embodiment is described withrespect to a particular feature. Examples of features provided in thedisclosure are intended to be illustrative rather than restrictiveunless stated otherwise. The above description is intended to cover suchalternatives, modifications, and equivalents as would be apparent to aperson skilled in the art having the benefit of this disclosure. Thescope of the present disclosure includes any feature or combination offeatures disclosed herein (either explicitly or implicitly), or anygeneralization thereof, whether or not it mitigates any or all of theproblems addressed herein. Accordingly, new claims may be formulatedduring prosecution of this application (or an application claimingpriority thereto) to any such combination of features. In particular,with reference to the appended claims, features from dependent claimsmay be combined with those of the independent claims and features fromrespective independent claims may be combined in any appropriate mannerand not merely in the specific combinations enumerated in the appendedclaims.

What is claimed is:
 1. A solar-tracking photovoltaic (PV) system,comprising: a driven support assembly including a motor drive mounted ona drive pile; a first torque tube extending along a longitudinal axisbetween a first driven end and a first free end, wherein the motor driveis coupled to the first driven end to rotate the torque tube about thelongitudinal axis; a torque tube coupler extending along thelongitudinal axis between a first end section and a second end section,wherein the first end section is coupled to the first free end, whereinthe torque tube coupler comprises a medial section between the first endsection and the second end section, wherein the medial section has adiameter greater than a diameter of the first and second end sections,and wherein the diameter of the medial section is approximately the sameas a diameter of the first torque tube; a second torque tube extendingalong the longitudinal axis, wherein the second torque tube includes asecond free end coupled to the second end section; and a solar modulemounted on the second torque tube and the torque tube coupler.
 2. Thesolar-tracking PV system of claim 1 further comprising a non-drivensupport assembly including a bearing assembly mounted on a non-drivepile, wherein the second torque tube is supported by the non-drivensupport assembly.
 3. The solar-tracking PV system of claim 1, whereinthe first end section of the torque tube coupler includes a couplercross-sectional area, wherein the first torque tube includes a tubecross-sectional area at the first free end, and wherein the couplercross-sectional area and the tube cross-sectional area are concentric.4. The solar-tracking PV system of claim 3, wherein the couplercross-sectional area and the tube cross-sectional area are annular. 5.The solar-tracking PV system of claim 4, wherein an outer diameter ofthe coupler cross-sectional area is less than an inner diameter of thetube cross-sectional area.
 6. The solar-tracking PV system of claim 4,wherein an inner diameter of the coupler cross-sectional area is greaterthan an outer diameter of the tube cross-sectional area.
 7. Thesolar-tracking PV system of claim 1, wherein the torque tube couplerincludes a medial section extending between the first end section andthe second end section, and wherein the medial section has a same outerdiameter as the torque tubes.